1. Field of the Invention
This invention relates to filtration systems. More particularly, this invention relates to a filter septum through which liquid to be filtered is passed and the method of manufacturing this filter septum.
2. State of the Art
The state of the prior art is accurately set forth in detail in a technical paper, of which I am a coauthor, entitled "MICROSCREEN FILTRATION OF METALWORKING FLUIDS" presented and published in March 1993 by the Society of Manufacturing Engineers. In this paper the term "microscreen" is defined as a thin metallic sheet with small, uniform apertures or holes throughout. This definition eliminates screens constructed of wire, plastic or synthetic fiber. The advantages of microscreen septums are also presented, centering around higher flux rates made possible by the ability to make the septum aperture smaller, more closely spaced, and more accurately defined by utilizing an electrochemical process in the manufacture of the microscreen. This microscreen is an essential part of the present invention.
As also presented in the above-mentioned paper, the difficulty utilizing the advantages of microscreen lies in the fabrication of the filter septum utilizing microscreen. Before the present invention, the most successful use of microscreen has been in placing the microscreen over the outside of a drum of perforated plate by wrapping and clamping the microscreen in position. The difficulties encountered in using only mechanical clamping to secure the microscreen to a perforated substrate or base plate are obvious even in the more successful use in drums and cylinders where often doctor blades are used for scraping and cleaning or pressure swings are used for backflow regeneration. With planar septum configurations the problems can be exasperated.